Surgical depth instrument

ABSTRACT

A depth gauge for measuring the depth of a hole in a bone is disclosed having a digital readout for providing the measurement to a surgeon. The depth gauge has a probe with a tip inserted into and positioned proximate to the depth the hole, and has a reference member adjustably positioned relative the probe and against the bone proximate the hole. A measuring device is provided with the depth gauge for measuring the relative distance between the tip and the reference member, and the measuring device has a large, digital display for providing the relative distance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 11/081,147, filed Mar. 16, 2005, which issued as U.S. Pat. No.7,165,336 on Jan. 23, 2007, herein incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The invention relates to an instrument for determining the depth of ahole and, in particular, a depth gauge for providing a digitalmeasurement of the depth of a hole in a bone.

BACKGROUND OF THE INVENTION

Many surgical procedures utilize surgical devices secured to the bone ofa patient. In some instances, a bone plate may be utilized that spansand secures together one or more bones or pieces thereof. In otherinstances, a screw or other fastener may be fastened to a bone withoutanother device, such as a screw used to secure a transplanted tendon.

In many of these procedures, it is preferred to create a pilot hole inthe bone prior to securing the fastener in the bone. Oftentimes, thispreference arises from the importance of having a fastener that isinserted to a proper depth. That is, the opposite side of the bone fromthe drill site will typically be abutted by soft tissues that may beharmed if the screw is too long. As an example, a fastener mounted inthe pedicle portion of the human spine should not extend to a pointwhere the fastener contacts the spinal cord itself; an event that cancause irreparable nervous system damage including paralysis.

In other examples, immediate short-term damage is not a significantissue from slight over-drilling because the tissue on the opposite sidewill heal quickly. Over-drilling through a metacarpal may simply resultin damage to the fat layer within the finger. However, if a screw isused that is too long, it may protrude and be tactilely felt by thepatient, or it may pierce the skin itself. In addition, the screw mayprevent soft tissues moving over the bone surface, such as tendons,ligaments, or muscles.

During drilling, the surgeon is typically capable of recognizing theresistance on the drill in order to determine when the drill haspenetrated through the bone. Because the simple act of drilling does notprovide an exact measurement of the depth of the bone itself, a depthgauge is commonly employed for directly measuring the depth of the holefrom the top, drilling side to the bottom, opposite side.

Currently, many designs are known and utilized for measuring the depthof a hole or bore in a portion of a bone. Generally speaking, thesedesigns utilize a central probe member having a barb at a distal end,and a sleeve or channel member. The probe member is inserted into thepilot hole while the surgeon attempts to find purchase with the barb.More specifically, the probe member is inserted to a depth greater thanthe depth of the pilot hole so that the barb is beyond the oppositeside, at which point the surgeon finds purchase by hooking the barb tothe opposite side.

The probe member is received in the sleeve or channel member and mayreciprocate relative thereto. The channel member has graduated markingsalong a portion of its length, typically in inches and/or millimeters. Amarker is laterally secured to the probe member such that, as the probemember shifts relative to the channel member, the marker indicates therelative shift between the probe member and the channel member.Accordingly, once the probe member has been secured to the opposite sideof the bone, the channel member is shifted relative to the probe memberand toward the bone until the channel member abuts the surface of thebone. The depth gauge is then read by examining graduated markingsindicated by the probe member marker.

A number of problems are experienced with this depth gauge. As aninitial point, the components are typically made with surgical-gradestainless steel, and the graduated markings are embossed therein.Therefore, the brightness of the operating room lights on the highlyreflective surface can make the markings difficult to read. The markingsare commonly in small increments, such as millimeters, and surgeonsoften have trouble differentiating between the markings, or notingpartial increments. Reading these gauges, then, often requires carefullyholding the depth gauge as the reading is taken, and a surgeon's effortto closely examine the reading may result in a loss of securement orpurchase of the barb on the bone, thus necessitating a re-measurementand a loss of time.

Proper reading of the markings requires a surgeon's eyes to be properlyaligned with the markings. That is, a proper view of the measurementrequires the surgeon to view the gauge from a lateral point of view sothat the view of the probe marker aligned with the graduated markings isproper not distorted by the surgeon's elevated, standing perspective.Therefore, it is often necessary for the surgeon to bend over whileusing these gauges to view an accurate reading. If the depth gauge istilted in order to make the reading, the sleeve will shift relative tothe probe, thus making the measurement inaccurate and possibly causingthe barb to become unsecured, as discussed above.

In addition, removing of the depth gauge often causes the measurement tobe lost. As the bone is essentially clamped, by light pressure, betweenthe distal end of the channel member and the distal barb of the probemember, it is often necessary to retract the channel member from thebone surface in order to extract the probe from the pilot hole.

Additionally, if such retraction were not necessary, it is stilldifficult to extract the barb of the probe member without altering themeasurement reading. Because the pilot hole has a relatively smalldiameter, and the probe member is relatively deflectable, a small amountof manipulation is required to remove the probe member. When thismanipulation is through cancellous bone, the barb may become snaggedwhile being extracted. These issues are compounded by the fact that thesurgical procedure often requires multiple screws, and surgeons preferto move quickly by taking their measurements, selecting their screws,and securing the screws in the pilot holes, each in rapid succession.Clearly, it would be difficult and unwise to rely on a surgeon's abilityto remove the depth gauge without altering the measurement provided inorder to make a selection of fastener length.

Accordingly, there has been a need for an improved depth gauge forsurgical procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, FIG. 1 is a perspective view of a form of a depthinstrument of the present invention in an engaged position with afragmentary bone portion in cross-section;

FIG. 2 is an exploded perspective view of the depth instrument; and

FIG. 3 is a rear perspective view of the depth instrument.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, a depth instrument 10 is depicted securedwith a bone portion 12 in order to measure the depth of a passageway inthe form of a bore or hole 14 formed therein for receiving a fastenersuch as a screw (not shown). As can be seen, the bone portion 12 isbi-cortical. That is, the bone portion 12 has a first, proximal corticallayer 16, a cancellous layer 18, and a second, distal cortical layer 20.However, it should be noted that the instrument 10 is suitable for usewith bone portions having other structures, such as those includingsolid cortical bone.

As described above, the hole 14 may be a pilot hole formed in the boneportion 14. In using the instrument 10 to measure the distance from aproximal surface 51 formed on the proximal cortical layer 16 to a distalsurface 52 formed on the distal cortical layer 20, the instrument 10operates such that the relative movement between two portionsrespectively abutting the proximal surface 51 and the distal surface 52provides a precise measurement of the distance there between. Theinstrument 10 includes a probe member 30 inserted into a proximalopening 32 of the hole 14, and through the hole 14 to a distal opening34 thereof such that a distal tip 36 of the probe 30 extends from thedistal opening 34.

The probe tip 36 includes a securement or catch in the form of a hook orbarb 38 for abutting the distal surface 52, as described above, the barb38 extending to a side of the probe tip 36. Once the barb 38 hascompletely passed through the distal opening 34, the instrument isshifted slightly in the direction that the barb 38 extends. A slightretraction of the probe 30 from the hole 14 allows the barb 38 to engagewith the distal surface 52 of the distal cortical layer 20 so that aninterference therewith is created. In this manner, the barb 38 and probe30 are relatively positioned against the bone portion 12 and, throughthe use of slight tension, are retained thereon.

The instrument 10 further includes a reference portion for abutting theproximal surface 51, the reference portion being in the form of a sleevemember 50. The sleeve member 50, as depicted, is a generally hollowcylindrical member with the probe 30 received in a reciprocating fashionwithin the sleeve member 50. The sleeve member 50 and, probe 30 areconcentrically arranged so that the sleeve member 50 abuts the proximalsurface 51 in a manner similar to that of a bone plate or fastener head,for instance. Accordingly, the sleeve member 50 and barb 38 cooperatesuch that their relative position (and therefore distance) provides anaccurate measurement of the depth of the hole 14 such that a screw orfastener may be selected whose length is accommodated by the hole 14 asdesired by the surgeon.

Once the barb 38 is positioned on the distal surface 52, the sleeve 50is moved towards the proximal surface 51 such that the sleeve 50 abutsthereagainst. The sleeve 50 is secured with or integrally formed with aninstrument body 60. In the present form, the sleeve 50 is secured firstto a knurled collar nut 60 that is received around a threaded nipple 62.The threaded nipple 62 is secured via a pair of screws 61 to the body60. Although the body 60 is depicted with graduated markings 64, themarkings 64 are unnecessary to the preferred operation of the instrument10.

With reference to FIG. 3, the body 60 includes a rear side 65 having achannel 66 formed therein. The channel 66 is aligned with the innercavity of the sleeve 50 such that the probe 30 extends through thesleeve 60 and into the channel 66. A proximal end 70 of the probe 30 issecured to a measuring member in the form of a slide member 72. In thepresently depicted form, the probe proximal end 70 is secured to theslide member 72 with a set screw 74. The set screw 74 may be removed toallow the instrument to be dismantled, such as for removal of tissueand/or autoclaving. In addition, a quick-release connection such as asnapping collar (not shown) may be provided on either the probe 30 orthe slide 72 providing a releasable connection therebetween.

The slide 72 is secured to the body 60 such that the slide 72 and probe30 may reciprocate relative to the body 60. In this manner, when thebarb 38 is secured on the distal surface 52, the slide 72 remainsstationary as the sleeve 50 and body 60 are moved toward and against theproximal surface 51.

The body 60 includes teeth 80 along one edge 82 thereof. The teeth 80cooperate with the slide 72 to provide a measurement of the movementbetween the slide 72 and the body 60. By way of example, suchcooperation between the body 60 and slide 72 is utilized in digitalcalipers, such as that made by Mitutoyo America Corporation, 965Corporate Blvd., Aurora, Ill., and by Guilin Measuring and CuttingWorks, 106 Chongxin Road, Guangxi, Guilin 541002, Peoples Republic ofChina.

The slide 72 includes a microprocessor (not shown), or the like, and adigital electronic display 90 such as a liquid crystal display orlight-emitting diode display. As the slide 72 moves relative to the body60, the display 90 presents the measured relative motion therebetween.As can be seen, the display 90 may provide the measurement in inches, ormillimeters, as selected by button 92. As the display 90 operates withelectricity, a cover 94 is provided for accessing a battery compartment.The display 90 automatically returns to a A0@ reading when turned on orwhen an AON@ button 96 is pushed. Power is shut off when an AOFF@ button98 is pushed. Furthermore, so that the reading is not lost duringextraction, a AHOLD@ button 100 is provided.

As can be seen, the display 90 has a large screen 102 presenting largenumerals 104 that indicate a measurement between the proximal and distalsurfaces 51, 52. Accordingly, the display 90 can easily be read by asurgeon. Furthermore, a surgeon may position the instrument 10 in thehole 14 for taking a measurement, depress the AHOLD@ button 100 totemporarily record the reading, remove the instrument 10 from the hole14, and then read the screen 102 on the removed instrument 10.

It should be noted that the display screen 102 may provide informationother than the dimensional measurement. For instance, a particularmanufacturer of surgical devices may provide the instrument 10 as partof a kit (not shown) including a bone plate that mates with a head andshank formed on a screw. The slide 72 may be calibrated to compensatefor a portion of the screw head and shank received within the boneplate. Accordingly, the screen 102 may suggest a proper screw for usewith the bone plate. The display 90 may also provide an indication thatthe reading is not stable because the sleeve 50 and probe 30 are notgenerally stationary relative to each other, such as in the event thatcompressible soft tissue is caught on the barb 38 or between the sleeve50 and the proximal surface 51, or in the event the barb 38 is notsecurely positioned.

It should be noted that the instrument probe 30 may be provided withoutthe barb 38. As an example, the probe tip 36 may be inserted to a depthsuch that the tip 36 is coincident with, but generally does not extendthrough, the distal opening 34 of the hole 14. For instance, a surgeonmay place a stop or finger on the distal surface 52 of the bone 14 torecognize with the probe 30 has reached the distal opening.

While the invention has been described with respect to specific examplesincluding presently preferred modes of carrying out the invention, thoseskilled in the art will appreciate that there are numerous variationsand permutations of the above described systems and techniques that fallwithin the spirit and scope of the invention as set forth in theappended claims.

1. An electronic instrument for measuring the depth of a bore, theinstrument comprising: a generally cylindrical sleeve, a probe which isdisposed for reciprocating movement within the sleeve, the probe havinga radially extending protrusion near the tip, an electronic sensor thatgenerates an electrical signal relating to the distance between the tipof the sleeve and the protrusion of the probe, a display which receivesa signal from the sensor and display information relating relating tothe distance between the end of the sleeve and the protrusion of theprobe.
 2. The electronic instrument of claim 1 wherein the display is anelectronic digital display.
 3. The electronic instrument of claim 2wherein the electronic digital display is a liquid crystal display. 4.The electronic instrument of claim 1 wherein the diameter of the probeat the radially extending protrusion is smaller than the diameter of thebore.
 5. The electronic instrument of claim 2 wherein the electronicdigital display displays a numerical representation of the distancebetween the end of the sleeve and the protrusion of the probe.
 6. Theelectronic instrument of claim 2 wherein the electronic digital displaydisplays information relating to a fastener to be secured within thebore.